The invention relates to a hydraulic fine blanking head for a mechanical press, specifically a fine blanking press, which is supported by a head piece mounted on a press machine frame above a ram, which ram supports a table top and executes a stroke movement in axial alignment to its stroke axis, with a flange inserted into the head piece with a tube-like design, the shoulder of which fine blanking head is fixed by screwed connections at the side of the head piece facing the ram. The head piece includes a tube-like main cylinder with pistons and pins positioned inside thereof, with, the main cylinder being pressure tight and closed with a cover or a retaining plate, and a hydraulic system for feeding the main cylinder with a pressure fluid adjusted to a desired pressure.
The invention further relates to a method for infeeding a high pressure hydraulic fluid to a hydraulic fine blanking head in a press, specifically a fine blanking press, wherein an adjustable pressure is applied through a hydraulic fluid fed to the fine blanking head from a high pressure source to pistons retained in the main cylinder, which produces a pressure and/or deformation force, which actuates the press ram mechanically or hydraulically.
DE 1 279 622 A1 discloses a fine blanking press with a cutting piston, a plunger piston pressing a sheet metal workpiece onto the bedplate of the press and a pressure piston supporting the part of the workpiece that is to be cut out, wherein the head of the press is provided with an adjusting spindle for adjusting a stopping flange that limits the stroke of the movable yoke at the upper side. The limiting/stopping of the movable yoke is adjusted by turning threaded cylinders running one in another. The fine adjustment of the thread is carried out by means of a handwheel via a worm to a toothed wheel directly attached to the bottom of the outer threaded cylinder, whereas a quicker, less fine adjustment is provided by an electrical motor driving the worm via two bevel gears.
Height adjustment of the cutting head due to the manual operation as described above does not permit a sufficient adjusting and infeed accuracy regarding the height position of the head. In addition it is of disadvantage that the repeating accuracy of the adjustment is low, such that the quality of the fine blanked parts suffers.
A further disadvantage is that a spindle distortion due to the normally existing axial backlash between the cylinders can not be excluded.
Other known solutions for adjusting the distance between a press upper tool fixed to a ram, working together with a press lower tool fixed to a bedplate, and the ram use arrangements of pressure wedges (DE 2 039 644 A1) or hydraulically actuated cylinders (DE 198 22 436 A1). However, these known solutions due to the cooperation of cutting piston, V-shaped projection piston and V-shaped projection pins are not suitable for fine blanking presses.